Gastric bypass leads to improvement of diabetic neuropathy independent of glucose normalization--results of a prospective cohort study (DiaSurg 1 study).

Müller-Stich, Beat P; Fischer, Lars; Kenngott, Hannes G; Gondan, Matthias; Senft, Jonas; Clemens, Gabriella; Nickel, Felix; Fleming, Thomas; Nawroth, Peter P; Büchler, Markus W

OBJECTIVE Surprisingly, 40% to 95% of patients with type 2 diabetes mellitus (T2DM) show early remission of hyperglycemia after obesity surgery. It is unknown to what extent other diabetes-associated comorbidities such as distal peripheral neuropathy (DPN) might be influenced by obesity surgery. This pilot study aimed at providing further evidence for the impact of Roux-en-Y gastric bypass (RYGB) on both glycemic control and DPN in non-severely obese patients with insulin-dependent T2DM. METHODS In the present prospective cohort study, 20 patients with long-standing, insulin-dependent T2DM and a body mass index (BMI) between 25 and 35 kg/m underwent laparoscopic RYGB. Body mass index, glycosylated hemoglobin (HbA1c), and DPN [quantified by the Neuropathy Symptom Score (NSS) and the Neuropathy Deficit Score (NDS)] were investigated. RESULTS Six months after surgery, the preoperative BMI of 32.8 ± 2.1 kg/m (mean ± standard deviation) dropped to 25.6 ± 2.5 kg/m (P < 0.001). Preoperative HbA1c levels decreased from 8.5 ± 1.2% to 7.1 ± 1.2% (P < 0.001), with 15% of patients having a normalized HbA1c level lower than 6.2%. Of 12 patients with documented DPN, the median NSS was 8 (range, 0-10) preoperatively and 0 (range, 0-9) postoperatively (P = 0.004), with 8 patients scoring an NSS of 0. The median NDS was 6 (range, 2-8) preoperatively and 4 (range, 0-8) postoperatively (P = 0.027), with 1 patient scoring an NDS of 0. All patients had an improvement or normalization in either 1 or both scores. CONCLUSIONS As expected, BMI and HbA1c levels improved significantly after RYGB. More interestingly, neuropathy scores, such as NSS and NDS, improved significantly early after surgery. Symptomatic neuropathy was completely reversible in 67% of the patients. These findings add further evidence to the fact that RYGB might be a valuable treatment option not only for improving glycemic control but also for reducing diabetes-associated comorbidities, such as DPN. This points to a complex metabolic effect of RYGB that exceeds glucose normalization. However, the results still need to be confirmed in controlled trials.